1. Field of the Invention
The present invention relates to a recording apparatus having a stepping motor as an actuator, particularly to a recording apparatus equipped with a sleep mode for suppressing power consumption at the time of software power off.
2. Related Background Art
In recent years, with an increasing demand for reduction of power consumption, a machine provided with a sleep mode has been developed in which an unnecessary circuit is not operated in a software power off state, and CPU clock is further lowered to suppress the power consumption. Additionally, there has also been a machine in which only a pilot lamp for informing a user is turned off even in the software power off state. The machine is on standby while the power consumption is substantially unchanged. However, this cannot be assumed to be placed in the sleep mode.
In a recording apparatus using a stepping motor as an actuator, even when the device is started from either a hardware power on state or from a sleep mode, a motor mechanical phase (angle) (rotor position) is not seen. Therefore, to equalize a motor electrical phase (angle) (exciting phase) with the mechanical phase, pulses for one or more cycles are inputted at a low frequency within an automatic starting area and in at least the electrical phase to perform phase alignment.
The states of the electrical and mechanical phases during starting are shown in FIGS. 10A to 10D. In the drawings, for the description, it is assumed that the motor is driven in two-phase excitation and stopped in two phase positions without considering any detent. An arrow indicates the electrical phase (exciting phase), and ∇ indicates the mechanical phase. In FIG. 10A, since the electrical phase is equal to the mechanical phase, the device smoothly starts up without causing any positional deviation. In FIGS. 10B and 10D, however, since the electrical phase deviates from the mechanical phase by 90 degrees, positional deviation occurs by this phase difference during starting. Furthermore, when through-up occurs excessively steeply, loss of synchronism occurs in worst cases. In FIG. 10C, since the phase difference is 180 degrees, there is a high possibility that not only the positional deviation but also the loss of synchronism occurs. To avoid the worst situation of loss of synchronism, as described above, the phase alignment has been performed which comprises inputting the pulses for one or more cycles at the low frequency within the automatic starting area in which there is a sufficient torque and in at least the electrical phase to equalize the electrical phase with the mechanical phase.
In the conventional method, however, when the electrical and mechanical phases of the stepping motor are actually different from each other, a targeted effect can be obtained. However, the phase alignment is performed even during starting from the state of FIG. 10A (the electrical phase is equal to the mechanical phase). Therefore, when some pulses of low frequencies are inputted in the automatic starting area where there is a sufficient torque, noise or slight vibration is unfavorably generated.